First Report of Lasiodiplodia theobromae Causing Rot in Eggplant Fruit in Brazil

Eggplant (Solanum melongena) is one of the main Solanaceae species cultivated and consumed in Brazil. In March 2017, three eggplant fruit (cv. Ciça) collected from field production in Chã Grande, Pernambuco state, Brazil, presented circular rot lesions, mildly depressed, starting at the apex, extending to the entire fruit in 5 days with an abundance of gray mycelia and with some pycnidia releasing striated and brown conidia. After morphological analysis, the fungus was identified as Lasiodiplodia sp. Three single-spore isolates were obtained and deposited in the culture collection “Micoteca URM Profa. Maria Auxiliadora Cavalcanti” at the Universidade Federal de Pernambuco (Recife, Brazil), as URM7678, URM7679, and URM7707. For morphological analysis, culture sporulation was induced as described by Machado et al. (2014). The main morphological characteristics include conidia, initially hyaline, becoming dark brown and striated at maturity, one-septate, thick walled, and ellipsoid, 20.8 to 23.4 × 11.7 to 13 µm (n = 30). Based on these characteristics and compared with previous morphological descriptions (Alves et al. 2008), the fungus was identified as Lasiodiplodia theobromae. To confirm species identification, genomic DNA was extracted, and sequences of the internal transcribed spacer of the rDNA and translation elongation factor 1-α (TEF1-α) (Alves et al. 2008) were obtained for the three isolates and deposited in GenBank (accession nos. MG813266 to MG808271). According to BLAST search, the TEF1-α sequences showed 99% identity with sequences of the type strain L. theobromae CBS164.96 (AY640258). A combined phylogenetic tree obtained by Bayesian inference using MrBayes version 3.1.1 (Ronquist and Huelsenbeck 2003) grouped the isolates within the L. theobromae clade, and the identification was confirmed. Koch’s postulates were conducted by inoculating five asymptomatic eggplant fruit (cv. Ciça) previously disinfested with 0.5% hypochlorite and unwounded or superficially wounded with a sterile needle at two equidistant points, with mycelial disks or conidia suspension. Potato dextrose agar (PDA) plugs (6-mm diameter) were taken from 7-day-old colonies and deposited on the wounds. PDA plugs were used as a control. For conidia inoculation, culture sporulation was induced as described by Machado et al. (2014). Ten microliters of a conidia suspension (4.7 × 10⁵ conidia/ml) was pipetted on the inoculation sites. Sterile distilled water was used as a control. The inoculated fruit were maintained in plastic boxes that contained a piece of moistened cotton wool and were maintained in a moist chamber at approximately 25°C for 6 days. In wounded fruit, the first symptoms developed 2 days after inoculation and presented discoloration or circular, mildly depressed lesions on the inoculation sites. After 6 days, a gray mycelia of the fungus had covered the entire fruit surface and caused internal, black, dry rot. The inoculated fungus was reisolated, confirming Koch’s postulates. The control and unwounded fruit remained asymptomatic. L. theobromae is a Botryosphaeriaceae fungus of great phytopathological importance with broad distribution that causes several diseases in a wide host range (Slippers and Wingfield 2007), including rot in eggplant fruit (Woodward et al. 2005). To our knowledge, this is the first report of L. theobromae causing fruit rot in eggplant fruit in Brazil.